Stupid rule, but there *MAY* be a way to make it work: Just list the information for each individual item on a board (per pizza or per slice), and let the millennials use their smartphone calculator to figure it out themselves.
Nevermind, it means they would have to actually DO something...
In a true direct democracy each of us has a vote. Each of us that wants the detailed menu votes with our feet and money for that option. Each of us that wants to waive the detailed menu votes with our feet and money for that option.
We have a new vote each hour of each day.
Direct Democracy. Problem solved.